A man rides a bicycle near damaged buildings in the rebel held besieged al-Sukkari neighbourhood of Aleppo, Syria October 19, 2016. REUTERS/Abdalrhman Ismail - RTX2PJSA

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BEIRUT (Reuters) - The United Nations has abandoned plans to evacuate patients from besieged rebel-held east Aleppo which it had hoped to accomplish during a three day lull in fighting last week, blaming all parties to the conflict for obstructing efforts.

"The evacuations were obstructed by various factors, including delays in receiving the necessary approvals from local authorities in eastern Aleppo, conditions placed by non-state armed groups and the government of Syria's objection to allowing medical and other relief supplies into the eastern part of the city," U.N. Under-Secretary-General for humanitarian affairs and emergency relief coordinator Stephen O'Brien said in a statement on Monday.

O'Brien said no patients and family members were evacuated during the three-day Russian unilateral ceasefire last week which ended on Saturday with a resumption of air strikes and a surge in ground fighting.

"I am outraged that the fate of vulnerable civilians – sick and injured people, children and the elderly, all in need of critical and life-saving support – rests mercilessly in the hands of parties who have consistently and unashamedly failed to put them above narrow political and military interests," he said.

The U.N. has been unable to access east Aleppo since July, when Syrian government and allied forces put the eastern part of the city under siege.